# Octopus Daikin Altherma 9kW to 8kW swap **URL:** \ **Category:** Heatpump\ **Created:** [6 March 2025 15:53 UTC](https://community.openenergymonitor.org/t/octopus-daikin-altherma-9kw-to-8kw-swap/28179 "2025-03-06T15:53:20Z")\ **Posts on this page:** 1\ **Showing post:** 27
**Author:** ![simon\_sh](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/simon_sh/32/30724_2.png) [@simon\_sh](https://community.openenergymonitor.org/u/simon_sh)\ **Post date:** [11 March 2025 10:29 UTC](https://community.openenergymonitor.org/t/octopus-daikin-altherma-9kw-to-8kw-swap/28179/27 "2025-03-11T10:29:55Z")
This is exactly what I’m experiencing with my 9kw Daikin. Heat punk estimates circa 5-6kw heat loss but I’d like the 8kw so it has additional overhead but can modulate down to the same minimum as the 6kw. During the January cold snap when it averaged -4 degrees overnight and -5.9 at the coldest point the heat loss was ~5kw. I believe the root cause having spoken to Octopus is assumptions / default air change rates which don’t reflect reality. > [@Measuring air change rates with CO2 sensors for heat pump heat loss calculation](https://community.openenergymonitor.org/t/measuring-air-change-rates-with-co2-sensors-for-heat-pump-heat-loss-calculation/25817): > > I’ve written a piece on measuring air change rates with CO2 sensors for the heat pump section in the OpenEnergyMonitor docs here: [https://docs.openenergymonitor.org/heatpumps/measuring\_ach\_with\_co2.html](https://docs.openenergymonitor.org/heatpumps/measuring_ach_with_co2.html). As some of you already know this has been a bit of a research interest for me and several other folk over recent months, in particular @AndrewC, Michael de Podesta, see his blog [Estimating Rates of Air Change in Homes | Protons for Breakfast](https://protonsforbreakfast.wordpress.com/2021/06/06/estimating-rates-of-air-change-in-homes)@Zapaman, and @glyn.hudson. @borpin I know it’s als… --- _[View the full topic](https://community.openenergymonitor.org/t/octopus-daikin-altherma-9kw-to-8kw-swap/28179)._